Hey, I'm no expert but I think there are a number of contributing factors to this. In my opinion, the disparity likely began due to the history of OT and has been perpetuated by a number of additional factors. OT began as a largely female-dominant field and therapy vocations tend to be female-dominant in general, albeit the specific male-female ratios obviously vary between different disciplines. In addition, OT is somewhat of an esoteric field, at least in the eyes of the general public so that may also contribute to the lack of males. Another possible contributing factor is that in some cases gender norms may be deterring to some males as they may not want to be associated with a profession that is perceived as a women's vocation. This last point sounds very inane, but you would be surprised how salient of a factor gender norms are to some people.
This is just my opinion based on speculation, but I'm fairly certain these are some possible explanations.
